MC 3 CHAP 5&6

• FIVE(5) KINGDOM CLASSIFICATION (ROBERT WHITTAKER)


  • ANIMALIA
  • PLANTAE
  • PROTISTA: single celled eukaryotes
  • FUNGI: fungus-like and related eukaryotic organisms
  • MONERA(Prokaryotes)
• Protista


  • algae, amoeba, euglena, paramecium slime moulds, plasmodium. Protozoans
• Fungi


  • fungus-like and related eukaryotic organisms, yeast, molds, mushrooms
• They are found in the soil, in the water, and on plants and animals. In fact, billions are found in humans on the skin and in both the nasal and intestinal tracts.
• Although most microorganisms live in harmony with the human body, some—called pathogens—can infect the body and cause disease. Infectious diseases range from mild illnesses, such as a cold, to fatal illnesses, such as AIDS.
• We occasionally encounter people or animals that are infected and thus expose ourselves to the pathogens of their diseases. In fact, our environment is such that everyday we live with some risk of exposure to diseases.
• Infection Disease Process


  The interaction between the pathogenic microorganism, the environment, and the host
• SIX (6) LINKS OF INFECTION PROCESS


  • PATHOGEN / MICROORGANISM
  • RESERVOIR
  • PORTAL OF EXIT
  • MODE OF TRANSMISSION
  • PORTAL OF ENTRY
  • SUSCEPTIBLE HOST
• PATHOGEN / MICROORGANISM

  • Viruses
  • Bacteria
  • Fungi
  • Parasitic protozoan diseases
  • Prions
• Pathogen

  • Pathogenicity - its ability to produce disease
  • Degree of virulence - its severity or harmfulness
  • Invasiveness - its tendency to spread
• Reservoir


  The principal habitat in which a pathogen lives, flourishes and can multiply
• Human reservoirs

  • Acute clinical cases
  • Carriers
• Types of carriers

  • Incubatory carriers
  • Inapparent carriers
  • Convalasecent carriers
  • Chronic carriers
• Examples of animal or insect reservoirs include Lyme disease (which is transmitted via ticks); Rabies (which is transmitted by dogs, cats, foxes and bats); and Salmonella (which is transmitted by poultry, cattle, sheep and pigs).
• Any infectious disease that is transmitted under natural conditions from animal to human is referred to as zoonosis.
• The environment contains a large number of reservoirs of infection, including soil (which acts as a reservoir for Clostridium tetani, the causative agent of tetanus) and water (which is a reservoir for Legionella pneumophila, the causative agent of Legionnaire's disease).
• Portals of exit

  • Alimentary
  • Genitourinary
  • Respiratory
  • Skin
  • Trans-placental
• Modes of transmission

  • Direct transmission
  • Indirect transmission
• Portals of entry

  • Inhalation (via the respiratory tract)
  • Absorption (via mucous membranes such as the eyes)
  • Ingestion (via the gastrointestinal tract)
  • Inoculation (as the result of an inoculation injury)
  • Introduction (via the insertion of medical devices)
• Susceptible host

  • Age
  • Presence of malnutrition or dehydration
  • Underlying chronic disease
  • Immobility
  • Medication which could disrupt or suppress their immune response
  • General resistance factors (such as mucous membranes, skin, cough reflex etc) that can help defend against infection
• The healthcare environment can expose patients to infection risks that they may not encounter elsewhere.
• Understanding how infections become established, and how they are transmitted, is essential for effective infection prevention and control.
• Pathogenicity


  The capability of a microorganism to cause a disease in a host; an innate property. Disease warning signs are often the result of toxic of allergic reactions.
• Virulence


  The quantity of pathogenicity of a microbe or a measure of the ability of the microbe to cause disease. Virulence is determined by the factors of invasiveness and toxigenicity.
• To cause disease, pathogens must penetrate the host tissues and multiply. Usually, they become localized and form a small focus of infection. In some cases, secretion is produced, and is called PYOGENIC infection.
• Within the body, localization usually occurs within the lymph nodes, liver, spleen or kidney. From this area of infection microbes may pass into the bloodstream and set up the conditions of BACTEREMIA (non multiplying bacteria in the blood stream.) and SEPTICEMIA (reproducing bacteria)
• Specific virulence factors

  • Adhesion factor
  • Invasiveness
  • Growth and survival enhancing factors
  • Infective dose
  • Toxigenicity
• Adhesins


  Specific virulence factors that enhance the ability of a microorganism to attach to the surface of mammalian proteins or polysaccharides
• Invasiveness


  The ability of microorganism to invade human tissues and to reproduce or multiply within the cells and tissues of the human body
• Growth and survival enhancing factors


  The ability of the bacteria to grow within the blood of the host utilizing the available iron
• Infective dose


  The amount or quantity of microorganisms required to produce disease symptoms in a host; the more virulent the microbe, the fewer the number needed
• Toxigenicity


  The ability of a microorganism to produce toxins
• Types of toxins

  • Endotoxin
  • Exotoxins
  • Neurotoxin
  • Enterotoxins
  • Cytotoxin
• Economic, medical and social factors, genetics or individual lifestyle choices can contribute to tipping the balance for or against microbial initiation of disease in a particular individual. Virtually any microorganism can cause disease under the right set of conditions.
• The common saying " when you are tired and run-down you are more prone to infection. ," this is because an infecti
• ENDOTOXIN


  Lipopolysaccharide component of gram-negative bacterial cell wall. Released when gram-negative bacteria die and their cell walls disintegrate.
• EXOTOXINS


  Protein toxins produced from various gram-negative and gram-positive pathogenic bacteria; released by growing cells.
• NEUROTOXIN


  Protein exotoxins that interfere with the functioning of the nervous system; usually work by blocking nerve cell transmissions.
• ENTEROTOXINS


  Stimulate the cells of the gastrointestinal tract in an abnormal way, which then causes inflammation of the tissues.
• CYTOTOXIN


  Protein exotoxins that kill cells by enzymatic attack or by blocking essential cellular metabolism; interfere with cellular functions (e.g. Hemolysin - lipids and proteins that cause lysis of red blood cells by disrupting the cell membrane, extremely common in E. coli infections).